The National Football League conducted a two-decade campaign to deny a growing body of scientific research that showed a link between playing football and brain damage, according to a new book co-authored by a pair of ESPN investigative reporters.

The book, "League of Denial: The NFL, Concussions and the Battle for Truth," reports that the NFL used its power and resources to discredit independent scientists and their work; that the league cited research data that minimized the dangers of concussions while emphasizing the league's own flawed research; and that league executives employed an aggressive public relations strategy designed to keep the public unaware of what league executives really knew about the effects of playing the game. ESPN The Magazine and Sports Illustrated published book excerpts on Wednesday morning.

The NFL's whitewash of the debilitating neurological effects of playing football suffered by players began under former commissioner Paul Tagliabue, who left office in 2006, but continued under his successor, current commissioner Roger Goodell, according to the book written by ESPN investigative reporters Mark Fainaru-Wada and Steve Fainaru.

The book, which will be released Tuesday by Crown Archetype, compares the NFL's two decades of actions on health and safety to that of Big Tobacco -- the group of cigarette-making corporations whose executives for years covered up the fact their products contained dangerous, addictive, potentially deadly and cancer-causing chemicals.

"There are many differences," the Fainaru brothers write in "League of Denial," "but one is that football's health crisis featured not millions of anonymous victims but very public figures whose grotesque demises seemed almost impossible to reconcile with their personas."

NFL executives declined to cooperate with the authors on the book. On Wednesday morning, league spokesman Greg Aiello declined to comment.

Among the major findings in "League of Denial," which the Fainarus spent more than a year researching and writing:

• Two original members of a concussion committee established by Tagliabue disavowed the committee's major findings, including the NFL's assertion that concussions were minor injuries that never led to long-term brain injury.

• As far back as 1999, the NFL's retirement board paid more than $2 million in disability payments to former players after concluding football gave them brain damage. But it would be nearly a decade before league executives would publicly acknowledge a link.

• Beginning in 2000, some of the country's top neuroscientists warned the NFL that football led to higher rates of depression, memory loss, dementia and brain damage.

• The league in 2005 tried unsuccessfully to have medical journals retract the published work of several independent concussion researchers.

• Independent researchers directly warned Goodell about the connection between football and brain damage in 2007, but the commissioner waited nearly three years to acknowledge the link and to dismantle the league's discredited concussion committee. In 2009, two other independent researchers delivered still more evidence that football caused brain damage during a private meeting at the NFL's Park Avenue headquarters. Yet the league committee's co-chairman, Dr. Ira Casson, mocked and challenged the researchers so aggressively that he offended others who were present, including a Columbia University suicide expert and a U.S. Army colonel who directed the Defense and Veterans Brain Injury Center.

• As the crisis escalated, the NFL tried desperately to regain control of the issue and contain damage to its brand. Before an October 2009 hearing on football and brain injuries conducted by the House Judiciary Committee, the NFL lobbied successfully to prevent Goodell from testifying on the same panel as the father of a high school quarterback who had died after sustaining a concussion.

• Dr. Ann McKee, the leading expert on football and brain damage, told the authors that she believes the incidences of neurodegenerative disease among NFL players will prove to be "shockingly high" and that "most NFL players are going to get this. It's just a question of degree." Since 2005, when the disease was first diagnosed in deceased NFL players, McKee has studied 54 brains harvested from deceased NFL players. All but two had chronic traumatic encephalopathy (CTE). "I'm really wondering where this stops," she told the Fainarus. "I'm really wondering if every single football player doesn't have this."

The health of former players and the league's previous scientific exploration formed the basis of a lawsuit filed against the NFL by more than 4,500 ex-players. The players charged that the league's Mild Traumatic Brain Injury Committee conducted fraudulent research to hide the connection between football and brain damage. On Aug. 29, the NFL and the former players settled the lawsuit for $765 million.

Former longtime New York Jets defensive lineman Marty Lyons, who is being inducted into the team's Ring of Honor on Oct. 13, was asked Wednesday about the issue of whether the league downplayed the concussion issue.

"I'm not going to accuse the league. You'd come off to the sideline [during a game] and maybe they wouldn't use the words 'You got a concussion.' You got dinged. Many times, they'd say, 'How many fingers?' You'd say three, and they'd say, 'Yeah, that's close enough' and you'd go back in," Lyons told ESPNNewYork.com's Rich Cimini. "That was by choice. That wasn't doctors or trainers saying, 'You're OK.' They would tell you to sit on one side of the bench and they would go look at other players. Next thing you'd know, you'd be back out there on the field. Players had to be more responsible for their own actions. I'm not saying the league didn't know, I'm not saying the players didn't know. It was part of the game."

One of the most significant findings in the book, for which the authors say they conducted more than 200 interviews and reviewed thousands of pages of previously undisclosed documents, traces how the league handled research under Tagliabue's guidance.

In 1994, Tagliabue established the Mild Traumatic Brain Injury Committee to act as the league's concussions investigatory committee. According to the book, the committee published its controversial research in a medical journal, "Neurosurgery," that was edited by a consultant to the New York Giants. The Fainarus write that the consultant, USC neurosurgeon Dr. Michael Apuzzo, was a "sports guy wannabe" who frequently worked into conversations that he'd just had lunch with Tagliabue and was thrilled to stand on the sidelines during games.

Some of the studies the NFL had published in "Neurosurgery" had startling conclusions: Concussions were minor injuries; multiple concussions did not increase the risk of further injury; and football did not cause brain damage. "Professional football players do not sustain frequent repetitive blows to the brain on a regular basis," the NFL's doctors asserted, according to the book.

Often, the Fainarus write, Apuzzo ignored peer-reviewers' objections to the league research before rubber-stamping it into the journal. The actions led some concussion researchers to privately ridicule "Neurosurgery" as "The Official Medical Journal of the National Football League" and the "Journal of No NFL Concussions," the authors write. Apuzzo declined to be interviewed for the book; he also declined to be interviewed for this story.

Dr. Kevin Guskiewicz, a researcher who joined the league's new concussion committee after the NFL dismantled the MTBI group, rejected the "Neurosurgery" papers, which he described as "industry-funded research at its best," according to the book.

Dr. Mark Lovell, who directed the NFL's Neuropsychological Program for 16 years, told the book's authors that concussion committee leaders inserted provocative language in research papers after they had been read and approved by other members, including him. In one passage, Lovell called "stupid" a claim by league researchers that it was "unlikely that athletes who rise to the level of the NFL are concussion prone." He also said he did not write that sentence. When the Fainarus reminded Lovell that he was listed as an author, he replied: "No, no, no. I mean, is my name on that sentence?"

The book levels sharp criticism at the handling of the health and safety issue by Goodell, who succeeded Tagliabue in August 2006. The authors write that Goodell inherited a concussion mess from Tagliabue but that Goodell took nearly three years to acknowledge a link and moved slowly to publicly address the growing crisis.

The book also does not spare independent concussion researchers. The Fainarus write of conflicts of interest, eccentricities and ego clashes among the independent researchers who wanted a piece of the concussion research. What emerges is a tale of researchers seeking to be part of a morbid brain chase, the prize of which is not only medical prestige but also money in the form of millions of dollars in donations and grants for continued research.

Under Goodell, the NFL has been a major contributor to funding such research. In 2010, the NFL gave Boston University $1 million and designated the university's Center for the Study of Traumatic Encephalopathy as the league's preferred brain bank. The league also pledged to encourage retired players to donate their brains to BU. But in 2012, four months after the suicide of former San Diego Chargers linebacker Junior Seau, and after multiple former players had been diagnosed posthumously with CTE by Boston University researchers, the league distanced itself from BU and donated $30 million to the National Institutes of Health.

The book also describes how the league intervened in the scramble among researchers on who would be chosen to study Seau's brain, which would ultimately be diagnosed with CTE by the National Institutes of Health.

By relying on interviews, documents and private emails, the Fainarus describe the extent to which independent researchers felt pressured and harassed by the league. A neuropathologist named Ron Hamilton said the NFL attempted "to set up a barrier," to let "everybody know that [we] were just insane." Steve DeKosky, one of the nation's leading Alzheimer's experts, wrote in a private email to his colleagues that the NFL was "stunning in its hypocrisy."

The book also relates the story of Mike Webster, the ex-Pittsburgh Steelers center and member of Hall of Fame who was the first NFL player to be diagnosed with CTE. In the final years of his life, Webster frantically accumulated an arsenal of weapons and had seriously considered turning them on NFL officials, whom he blamed for his deteriorating mental condition, Webster's son told the authors.

"No Revenge, No Sir," Webster wrote in a rambling letter to his family not long before his death in 2002. "Not Revenge, But Reckoning."